The invention relates to an internal combustion engine having an exhaust gas turbocharger with an exhaust gas turbine in the engine exhaust duct and a compressor driven by the exhaust gas turbine and being arranged in the engine intake line.
The publication DE 198 57 234 C2 describes such a supercharged internal combustion engine, the exhaust gas turbine of which has a divided spiral duct with two separate exhaust gas flow passages, each exhaust gas flow passage being fed with exhaust gases from one cylinder bank respectively of the internal combustion engine via one exhaust pipe of the exhaust line. The two exhaust pipes are connected to one another by a valve device making it possible to direct exhaust gas from one to the other of the two exhaust pipes. In addition a bypass is provided which bypasses the exhaust gas turbine and can likewise be opened and closed by the valve device.
Exhaust gas is directed from one to the other of the two exhaust pipes particularly in the powered operating mode of the internal combustion engine, in order to equalize or limit the pressure in the exhaust pipes. The two exhaust gas flow passages in the exhaust gas turbine have different flow cross-sections so that a greater back pressure can be obtained in the exhaust pipe with the smaller exhaust gas flow cross-section than in the exhaust pipe with the larger exhaust gas flow cross-section. This greater back pressure can be utilized to advantage for an exhaust gas recirculation device, which comprises a recirculation pipe between the exhaust pipe for the pipe with the smaller exhaust gas flow cross-section and the intake line, together with a return valve arranged in the recirculation pipe. It is noted here, however, that particularly in high engine speed ranges the quantity of exhaust gas returned must be limited, which can be achieved by directing exhaust gas from one to the other of the two exhaust pipes.
On the other hand, there is also a bypass for bypassing the exhaust has turbine which is advantageously opened during engine braking, in order to be able to control the turbine inlet pressure of the exhaust gas and hence also the required engine braking power.
The publication DE 196 18 160 C2 discloses an internal combustion engine having an exhaust gas turbocharger, the exhaust gas turbine of which has two exhaust gas inlet flow passages, which are located upstream of the turbine wheel. The two exhaust gas inlet flow passages are each supplied with exhaust gas by an exhaust pipe from the cylinder outlets of the internal combustion engine and a recirculation pipe of an exhaust gas recirculation device, via which exhaust gas from the exhaust line is returned into the intake line in specific operating states of the internal combustion, branching off from the exhaust pipe supplying the smaller exhaust gas inlet flow passage. In the turbine housing upstream of the turbine wheel the two exhaust gas flow passages are separated by a dividing wall, into which a valve device is integrated, via which the two exhaust gas flow passages can each be connected to a bypass bypassing the turbine wheel. In this way the exhaust gas can be blown off, bypassing the turbine wheel.
The valve device is embodied as a rotary slide valve having a cylindrical valve body, in the valve outer casing with axially extending communication openings, which can be adjusted between an open position communicating with the exhaust gas flow passages, and a closed position. Rotation of the valve body results either in blowing-off, exhaust gas whereby the gas content in the two exhaust gas flows is discharged via the bypass, or in a separation of the two flows, in which blowing-off is prevented and the exhaust gas must flow through the turbine inlet passages into the turbine.
The configuration shown in DE 196 18 160 C2 on the other hand does not permit an equalization of pressure between the two exhaust pipes or the two exhaust gas flows. There is no valve body position with the two opposing, axially extending communication openings which will only permit and exhaust gas flow transfer but no blowing-off of exhaust gas.
The publication U.S. Pat. No. 6,223,534 B1 discloses an engine braking device for an internal combustion engine having an exhaust gas turbocharger, the exhaust gas turbine of which is also of two-flow design and can be connected by a valve device to a bypass line. The valve device comprises a hollow cylindrical valve body having communication openings, which in an open position of the valve body connect the exhaust gas flow passages to the bypass line.
Even in the arrangement of U.S. Pat. No. 6,223,534 B1, it is only possible either to blow off the content of both exhaust gas flow passages via the bypass line or to shut the valve device off, preventing blow-off and directing the exhaust gas flow of both exhaust gas flow passages to the turbine wheel. No further possible settings, and in particular flow transfers between the two exhaust gas flow passages, are provided.
Based on this state of the art, it is the object of the invention to use simple design measures to construct a supercharged internal combustion engine having a two-flow exhaust gas turbine, in such a way that it is possible, depending on the current operating state of the internal combustion engine, not only to direct exhaust gases from one to the other of the two exhaust gas flow passages, but also to blow these gases off through a bypass line bypassing the exhaust gas turbine.